We introduce a method of integrating Global Positioning System(GPS)and accelerometer data for high-rate seismogeodesy.This method is based on the GPS variometric approach which can obtain seismic waves in real time us...We introduce a method of integrating Global Positioning System(GPS)and accelerometer data for high-rate seismogeodesy.This method is based on the GPS variometric approach which can obtain seismic waves in real time using only the readily available broadcast products and a single receiver.Collocated 5 Hz GPS and 200 Hz accelerometer data from the 2010 M_(W) 7.2 EI Mayor-Cucapaph earthquake were analyzed to verify the effectiveness of this method.Results reveal that this method can provide broadband and more accurate displacements qualified to avoid the baseline drifting caused by strong motion.Moreover,this method can effectively avoid the aliasing problem present in the 5-Hz GPS waveforms.We therefore conclude that this method can be a powerful tool to capture seismic waves in real time,which is crucial to tsunami early warning and earthquake rapid response.展开更多
Based on Continuous GPS (CGPS) observation data of the Crustal Movement Observation Network of China (CMONOC) and the Sichuan Continuous Operational Reference System (SCCORS),we calculated the horizontal coseismic dis...Based on Continuous GPS (CGPS) observation data of the Crustal Movement Observation Network of China (CMONOC) and the Sichuan Continuous Operational Reference System (SCCORS),we calculated the horizontal coseismic displacements of CGPS sites caused by the 2013 Lushan Mw 6.6 earthquake.The results indicate that the horizontal coseismic deformations of CGPS stations are consistent with thrust-compression rupture.Furthermore,the sites closest to the epicenter underwent significant coseismic displacements.Three network stations exhibited displacements greater than 9 mm (the largest is 20.9 mm at SCTQ),while the others were displaced approximately 1-4 mm.展开更多
By inverting GPS data recorded at stations of the Crustal Movement Observation Network of China(CMONOC)near the 2013 Lushan Ms7.0 earthquake,we found a horizontal displacement of 22 mm at a site about 32 km SW of the ...By inverting GPS data recorded at stations of the Crustal Movement Observation Network of China(CMONOC)near the 2013 Lushan Ms7.0 earthquake,we found a horizontal displacement of 22 mm at a site about 32 km SW of the epicenter and vertical displacements of as much as 12.4 mm at several sites.The vertical displacements were generally uplift on the west side of the nearby Longmenshan fault zone and subsidence on the east side.We also found coseismic ionospheric disturbances about 0.5 to 0.9 TECU in amplitude that lasted for about one hour.展开更多
Usually, GPS observation provides direct evidence to estimate coseismic displacement. However, GPS stations are scattered, sparse and cannot provide a detailed distribution of coseismic displacement. Strong ground mot...Usually, GPS observation provides direct evidence to estimate coseismic displacement. However, GPS stations are scattered, sparse and cannot provide a detailed distribution of coseismic displacement. Strong ground motion records share the same disadvantages as GPS in estimating coseismic displacement. Estimations from In SAR data can provide displacement distributions; however, the resolution of such methods is limited by the analysis techniques. The paper focuses on estimating the coseismic displacement of the M_S7.0 Lushan earthquake on April 20, 2013 using a simulation of the wave field based on the elastic wave equation instead of a quasi-static equation. First, the media and source models were constructed by comparing the simulated velocity and the record velocity of the ground motion. Then simulated static displacements were compared with GPS records. Their agreement validates our results. Careful analysis of the distribution of simulated coseismic displacements near the fault reveals more details of the ground motion. For example, an uplift appears on the hanging wall of the fault,rotation is associated with the horizontal displacement, the fault strike and earthquake epicenter provide the main control on motion near the faults, and the motion on the hanging wall is stronger than that on the footwall. These results reveal additional characteristics of the ground motion of the Lushan earthquake.展开更多
In mountainous areas,landslides induced by destructive earthquakes are one of the main causes of human casualties,which is an important link in the chain of earthquake hazards.Earthquake-triggered landslides are mainl...In mountainous areas,landslides induced by destructive earthquakes are one of the main causes of human casualties,which is an important link in the chain of earthquake hazards.Earthquake-triggered landslides are mainly controlled by three factors,namely seismic property,topography,and geology.Many studies have been conducted on these controlling factors of earthquake-triggered landslides.However,little is known about the effect of coseismic displacement on the distribution of landslides under different slope aspects and slope angles,hindering our understanding of the mechanism of inducing landslides by the combination of surface displacement and slope geometry at the local scale and leading to controversial opinions about the abnormal number of earthquake-triggered landslides in several cases.Here,we took the 2008 Wenchuan M_(w) 7.9 earthquake in China,the 2015 Gorkha M_(w) 7.8 earthquake in Nepal,and the 2016 Kaikōura M_(w) 7.8 earthquake in New Zealand as examples to investigate the relationship between the distribution of large earthquake-triggered landslides and the three-dimensional (3D)coseismic displacement field.We divided the landslide-prone area around the epicenter into regular grids and calculated the 3D coseismic displacement in each grid according to the radar satellite images and slip distribution model.Then,the 3D coseismic displacement was projected to two coordinate systems related to the slope where the landslides were located for statistical analysis.We determined that the surface uplift perpendicular to the slope is more likely to induce landslides,particularly when combined with large slope angles.Meanwhile,the number of landslides will be significantly reduced where the subsidence occurs.Regardless of uplift or subsidence,landslides are more likely to occur when the direction of coseismic horizontal displacement is far from the slope.The larger the slope angles are,the greater the effects of horizontal displacement and slope aspect.A dominant slope aspect also exists for earthquake-triggered landslides,which is different from the mean slope aspect calculated from the background topography.This dominant aspect angle is related to the focal mechanism and striking angle of surface rupture.These results indicate that we can simulate the 3D coseismic displacement field from known fault location and earthquake mechanism and combine the topographic data for landslide risk assessment in earthquake-prone mountainous areas to minimize the damage caused by possible earthquake-triggered landslides.展开更多
On September 5, 2022, a magnitude Ms 6.8 earthquake occurred along the Moxi fault in the southern part of the Xianshuihe fault zone located in the southeastern margin of the Tibetan Plateau,resulting in severe damage ...On September 5, 2022, a magnitude Ms 6.8 earthquake occurred along the Moxi fault in the southern part of the Xianshuihe fault zone located in the southeastern margin of the Tibetan Plateau,resulting in severe damage and substantial economic loss. In this study, we established a coseismic landslide database triggered by Luding Ms 6.8 earthquake, which includes 4794 landslides with a total area of 46.79 km^(2). The coseismic landslides primarily consisted of medium and small-sized landslides, characterized by shallow surface sliding. Some exhibited characteristics of high-position initiation resulted in the obstruction or partial obstruction of rivers, leading to the formation of dammed lakes. Our research found that the coseismic landslides were predominantly observed on slopes ranging from 30° to 50°, occurring at between 1000 m and 2500 m, with slope aspects varying from 90° to 180°. Landslides were also highly developed in granitic bodies that had experienced structural fracturing and strong-tomoderate weathering. Coseismic landslides concentrated within a 6 km range on both sides of the Xianshuihe and Daduhe fault zones. The area and number of coseismic landslides exhibited a negative correlation with the distance to fault lines, road networks, and river systems, as they were influenced by fault activity, road excavation, and river erosion. The coseismic landslides were mainly distributed in the southeastern region of the epicenter, exhibiting relatively concentrated patterns within the IX-degree zones such as Moxi Town, Wandong River basin, Detuo Town to Wanggangping Township. Our research findings provide important data on the coseismic landslides triggered by the Luding Ms 6.8 earthquake and reveal the spatial distribution patterns of these landslides. These findings can serve as important references for risk mitigation, reconstruction planning, and regional earthquake disaster research in the earthquake-affected area.展开更多
Three M_(W)>7.0 earthquakes in 2020-2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone,including the Mw7.8 Simeonof thrust earthquake on July 22,2020,the M_(W)7.6...Three M_(W)>7.0 earthquakes in 2020-2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone,including the Mw7.8 Simeonof thrust earthquake on July 22,2020,the M_(W)7.6 Sand Point strike-slip earthquake on October 19,2020,and the M_(W)8.2 Chignik thrust earthquake on July 29,2021.The spatial and temporal proximity of these three earthquakes prompts us to probe stress-triggering effects among them.Here we examine the coseismic Coulomb stress change imparted by the three earthquakes and their influence on the subduction interface.Our results show that:(1)The Simeonof earthquake has strong loading effects on the subsequent Sand Point and Chignik earthquakes,with the Coulomb stress changes of 3.95 bars and 2.89 bars,respectively.The Coulomb stress change caused by the Sand Point earthquake at the hypocenter of the Chignik earthquake is merely around 0.01 bars,suggesting the negligible triggering effect on the latter earthquake;(2)The triggering effects of the Simeonof,Sand Point,and Chignik earthquakes on aftershocks within three months are not well pronounced because of the triggering rates of 38%,14%,and 43%respectively.Other factors may have played an important role in promoting the occurrence of these aftershocks,such as the roughness of the subduction interface,the complicated velocity structure of the lithosphere,and the heterogeneous prestress therein;(3)The three earthquakes caused remarkable coseismic Coulomb stress changes at the subduction interface nearby these mainshocks,with an average Coulomb stress change of 3.2 bars in the shallow region directly inwards the trench.展开更多
In the case of reverse drag of normal faulting, the displacement and horizontal extension are determined based on the established equations for the three mechanisms: rigid body, vertical shear and inclined shear. Ther...In the case of reverse drag of normal faulting, the displacement and horizontal extension are determined based on the established equations for the three mechanisms: rigid body, vertical shear and inclined shear. There are three sub-cases of basal detachment for the rigid body model: horizontal detachment, antithetic detachment and synthetic detachment. For the rigid body model, the established equations indicate that the total displacement on the synthetic base (D<sub>t2</sub>) is the largest, that on the horizontal base (D<sub>t1</sub>) is moderate, and that on the antithetic base (D<sub>t3</sub>) is the smallest. On the other hand, the value of (D<sub>t1</sub>) is larger than the displacement for the vertical shear (D<sub>t4</sub>). The value of (D<sub>t1</sub>) is larger than or less than the displacement for the inclined shear (D<sub>t5</sub>) depending on the original fault dip δ<sub>0</sub>, bedding angle θ, and the angle of shear direction β. For all original parameters, the value of D<sub>t5</sub> is less than the value of D<sub>t4</sub>. Also, by comparing three rotation mechanisms, we find that the inclined shear produces largest extension, the rigid body model with horizontal detachment produces the smallest extension, and the vertical shear model produces moderate extension.展开更多
A gas puff imaging(GPI)diagnostic has been developed and operated on EAST since 2012,and the time-delay estimation(TDE)method is used to derive the propagation velocity of fluctuations from the two-dimensional GPI dat...A gas puff imaging(GPI)diagnostic has been developed and operated on EAST since 2012,and the time-delay estimation(TDE)method is used to derive the propagation velocity of fluctuations from the two-dimensional GPI data.However,with the TDE method it is difficult to analyze the data with fast transient events,such as edge-localized mode(ELM).Consequently,a method called the spatial displacement estimation(SDE)algorithm is developed to estimate the turbulence velocity with high temporal resolution.Based on the SDE algorithm,we make some improvements,including an adaptive median filter and super-resolution technology.After the development of the algorithm,a straight-line movement and a curved-line movement are used to test the accuracy of the algorithm,and the calculated speed agrees well with preset speed.This SDE algorithm is applied to the EAST GPI data analysis,and the derived propagation velocity of turbulence is consistent with that from the TDE method,but with much higher temporal resolution.展开更多
The estimation of residual displacements in a structure due to an anticipated earthquake event has increasingly become an important component of performance-based earthquake engineering because controlling these displ...The estimation of residual displacements in a structure due to an anticipated earthquake event has increasingly become an important component of performance-based earthquake engineering because controlling these displacements plays an important role in ensuring cost-feasible or cost-effective repairs in a damaged structure after the event.An attempt is made in this study to obtain statistical estimates of constant-ductility residual displacement spectra for bilinear and pinching oscillators with 5%initial damping,directly in terms of easily available seismological,site,and model parameters.None of the available models for the bilinear and pinching oscillators are useful when design spectra for a seismic hazard at a site are not available.The statistical estimates of a residual displacement spectrum are proposed in terms of earthquake magnitude,epicentral distance,site geology parameter,and three model parameters for a given set of ductility demand and a hysteretic energy capacity coefficient in the case of bilinear and pinching models,as well as for a given set of pinching parameters for displacement and strength at the breakpoint in the case of pinching model alone.The proposed scaling model is applicable to horizontal ground motions in the western U.S.for earthquake magnitudes less than 7 or epicentral distances greater than 20 km.展开更多
A seepage-geomechanical coupled embedded fracture flow model has been established for multi-field coupled simulation in tight oil reservoirs,revealing the patterns of change in pressure field,seepage field,and stress ...A seepage-geomechanical coupled embedded fracture flow model has been established for multi-field coupled simulation in tight oil reservoirs,revealing the patterns of change in pressure field,seepage field,and stress field after long-term water injection in tight oil reservoirs.Based on this,a technique for enhanced oil recovery(EOR)combining multi-field reconstruction and combination of displacement and imbibition in tight oil reservoirs has been proposed.The study shows that after long-term water flooding for tight oil development,the pressure diffusion range is limited,making it difficult to establish an effective displacement system.The variation in geostress exhibits diversity,with the change in horizontal minimum principal stress being greater than that in horizontal maximum principal stress,and the variation around the injection wells being more significant than that around the production wells.The deflection of geostress direction around injection wells is also large.The technology for EOR through multi-field reconstruction and combination of displacement and imbibition employs water injection wells converted to production and large-scale fracturing techniques to restructure the artificial fracture network system.Through a full lifecycle energy replenishment method of pre-fracturing energy supplementation,energy increase during fracturing,well soaking for energy storage,and combination of displacement and imbibition,it effectively addresses the issue of easy channeling of the injection medium and difficult energy replenishment after large-scale fracturing.By intensifying the imbibition effect through the coordination of multiple wells,it reconstructs the combined system of displacement and imbibition under a complex fracture network,transitioning from avoiding fractures to utilizing them,thereby improving microscopic sweep and oil displacement efficiencies.Field application in Block Yuan 284 of the Huaqing Oilfield in the Ordos Basin has demonstrated that this technology increases the recovery factor by 12 percentage points,enabling large scale and efficient development of tight oil.展开更多
Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface r...Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface ruptures and secondary disasters surrounding the epicentral area is important for post-earthquake emergency and disaster assessments.High-resolution Maxar and GF-2 satellite data were used after the events to extract the location of the rupture surrounding the first epicentral area.The results show that the length of the interpreted surface rupture zone(part of)is approximately 75 km,with a coseismic sinistral dislocation of 2-3 m near the epicenter;however,this reduced to zero at the tip of the southwest section of the East Anatolia Fault Zone.Moreover,dense soil liquefaction pits were triggered along the rupture trace.These events are in the western region of the Eurasian Seismic Belt and result from the subduction and collision of the Arabian and African Plates toward the Eurasian Plate.The western region of the Chinese mainland and its adjacent areas are in the eastern section of the Eurasian Seismic Belt,where seismic activity is controlled by the collision of the Indian and Eurasian Plates.Both China and Türkiye have independent tectonic histories.展开更多
Objective:To observe the clinical effect of articular cavity injection combined with bite splint therapy for the treatment of anterior disc displacement without reduction(ADDWoR).Methods:The research subjects for this...Objective:To observe the clinical effect of articular cavity injection combined with bite splint therapy for the treatment of anterior disc displacement without reduction(ADDWoR).Methods:The research subjects for this study were 30 patients with ADDWoR treated in the temporomandibular joint specialist outpatient clinic from November 2018 to November 2019,with a disease duration of 1 to 6 months.The treatment group was treated with an articular cavity injection of sodium hyaluronate+bite splint.The control group was treated with a simple articular cavity injection of sodium hyaluronate.The two groups were followed up once every 2 weeks to evaluate the treatment effect and observe the clinical efficacy of the two groups.Statistical analysis was carried out using SPSS 24.0.t-test and general linear regression analysis were carried out to compare the data of both groups,andχ^(2)-test and binary logistic regression analysis were performed for pain index comparison.Results:There was no significant difference in terms of the efficacy of the treatment received by both groups.The mouth opening and joint pain of patients in both groups were significantly improved after treatment(P<0.001).Conclusion:Articular cavity injection of sodium hyaluronate and occlusal splint therapy are both effective and safe methods for treating ADDWoR.展开更多
On 22 nd May 2021(local time),an earthquake of M_(s)7.4 struck Maduo county in Qinghai Province,China.This was the largest earthquake in China since the 2008 Wenchuan earthquake.In this study,ascending/descending Sent...On 22 nd May 2021(local time),an earthquake of M_(s)7.4 struck Maduo county in Qinghai Province,China.This was the largest earthquake in China since the 2008 Wenchuan earthquake.In this study,ascending/descending Sentinel-1 and advanced land observation satellite-2(ALOS-2)synthetic aperture radar(SAR)images were used to derive the three-dimensional(3-D)coseismic displacements of this earthquake.We used the differential interferometric SAR(In SAR,DIn SAR),pixel offset-tracking(POT),multiple aperture In SAR(MAI),and burst overlap interferometry(BOI)methods to derive the displacement observations along the line-of-sight(LOS)and azimuth directions.To accurately mitigate the effect of ionospheric delay on the ALOS-2 DIn SAR observations,a polynomial fitting method was proposed to optimize range-spectrum-split-derived ionospheric phases.In addition,the 3-D displacement field was obtained by a strain model and variance component estimation(SM-VCE)method based on the high-quality SAR displacement observations.Results indicated that a left-lateral fault slip with the largest horizontal displacement of up to 2.4 m dominated this earthquake,and the small-magnitude vertical displacement with an alternating uplift/subsidence pattern along the fault trace was more concentrated in the near-fault regions.Comparison with the global navigation satellite system data indicated that the SM-VCE method can significantly improve the accuracy of the displacements compared to the classical weighted least squares method,and the incorporation of the BOI displacements can substantially benefit the accuracy of north-south displacement.In addition to the displacements,three coseismic strain invariants calculated based on the strain model parameters were also investigated.It was found that the eastern and western parts of the faults suffered more significant strains compared with the epicenter region.展开更多
The coscismic deformation produced by 1998 earthquake (M8 = 6.2) in Zhangbei-Shangyi of northern China is measured by the differential synthetic aperture radar interferometry (D-InSAR) technique using the European Rem...The coscismic deformation produced by 1998 earthquake (M8 = 6.2) in Zhangbei-Shangyi of northern China is measured by the differential synthetic aperture radar interferometry (D-InSAR) technique using the European Remote Sensing satellite (ERS) SAR data. Interferograms are constructed from the ERS-1/2 SAR data by the three-pass method. The line-of-sight displacement map indicates that the deformation center of the earthquake is located at E114°20’, N40°57’, with the maximum uplift of 25 cm. The extent of the displacement is around 300 km2. The focal mechanism and earthquake-induced structures are analyzed based on the spatial distribution of the deformation. The results give new insights into the seismic mechanism study.展开更多
Analysis of GEONET observations covering the entire territory of Japan shows that the great Tohoku-oki earthquake that occurred on March 11, 2011 off the east coast of Honshu in Japan caused an eastward movement of th...Analysis of GEONET observations covering the entire territory of Japan shows that the great Tohoku-oki earthquake that occurred on March 11, 2011 off the east coast of Honshu in Japan caused an eastward movement of the northern part of the island by as much as 5.3 m. The GPS data from TEONET in China were used to derive far-field coseismic displacements and to assess the impact of the Tohoku-oki earthquake on crustal deformation in eastern China. The results reveal that the coseismic horizontal displacements induced by the earthquake are the level of millimeters to centimeters in North and Northeast China, with a maximum of 35 mm. Strain analysis also indicates that the earthquake resulted in an increase in the tensile strain on the north-northeast trending faults in North and Northeast China. The tensile strain imposed on the Yilan-Yitong and Dunhua-Mishan faults is more significant than that imposed on the faults in North China; the maximum normal strain reaches about 40 nano-strain. Considering that the static Coulomb stress loaded on the faults is limited, its effect on the regional seismic activity may not be significant.展开更多
This paper presents the coseismic displacement and preseismic deformation fields of the Lushan MS7.0 earthquake that occurred on April 20,2013.The results are based on GPS observations along the Longmenshan fault and ...This paper presents the coseismic displacement and preseismic deformation fields of the Lushan MS7.0 earthquake that occurred on April 20,2013.The results are based on GPS observations along the Longmenshan fault and within its vicinity.The coseismic displacement and preseismic GPS results indicate that in the strain release of this earthquake,the thrust rupture is dominant and the laevorotation movement is secondary.Furthermore,we infer that any possible the rupture does not reach the earth’s surface,and the seismogenic fault is most likely one fault to the east of the Guanxian-Anxian fault.Some detailed results are obtainable.(1)The southern segment of the Longmenshan fault is locked preceding the Lushan earthquake.After the Wenchuan earthquake,the strain accumulation rate in the southeast direction accelerates in the epicenter of the Lushan earthquake,and the angle between the principal compressional strain and the seismogenic fault indicates that a sinistral deformation background in the direction of the seismogenic fault precedes the Lushan earthquake.Therefore,it is evident that the Wenchuan MS8.0 earthquake accelerated the pregnancy of the Lushan earthquake.(2)The coseismic displacements reflected by GPS data are mainly located in a region that is 230 km(NW direction)×100 km(SW direction),and coseismic displacements larger than 10 mm lie predominantly in a100-km region(NW direction).(3)On a large scale,the coseismic displacement shows thrust characteristics,but the associated values are remarkably small in the near field(within 70 km)of the earthquake fault.Meanwhile,the thrust movement in this70-km region does not correspond with the attenuation characteristics of the strain release,indicating that the rupture of this earthquake does not reach the earth’s surface.(4)The laevorotation movements are remarkable in the 50-km region,which is located in the hanging wall that is close to the earthquake fault,and the corresponding values in this case correlate with the attenuation characteristics of the strain release.展开更多
Based on continuous GPS observations within China as well as global GPS tracking network, a calculation has been made of far-field coseismic displacements associated with the December, 2004 (Mw = 9.3) and March, 2005 ...Based on continuous GPS observations within China as well as global GPS tracking network, a calculation has been made of far-field coseismic displacements associated with the December, 2004 (Mw = 9.3) and March, 2005 (Mw = 8.7) earthquakes. The far-field coseismic displacements are associated with the 2004 shock range more than 6000―7000 km in both north-south and east-west dimensions, and depict an undulated wave pattern of contraction and extension. The coseismic displacements associ-ated with the 2005 event, however, are distributed near the epicentral region, and the event itself may be an aftershock of the 2004 earthquake.展开更多
By using precise leveling data observed between 1985 and 2010 across the south section of the Longmenshan fault zone,and eliminating the coseismic displacements caused by the Wenchuan Ms 8.0 earthquake,the interseismi...By using precise leveling data observed between 1985 and 2010 across the south section of the Longmenshan fault zone,and eliminating the coseismic displacements caused by the Wenchuan Ms 8.0 earthquake,the interseismic vertical deformation field was obtained.The result shows that the Lushan region,located between the Shuangshi–Dachuan fault(front range of the Longmenshan fault) and the Xinkaidian fault(south section of the Dayi fault),is situated in the intersection zone of positive and negative vertical deformation gradient zones,indicating that this zone was locked within 25 years before the Lushan earthquake.Based on leveling data across the rupture zone surveyed between 2010 and 2013,and by eliminating the vertical deformation within 3 years before the earthquake,the coseismic vertical displacement was derived.The coseismic vertical displacement for the benchmark DD35,which is closest to the epicenter,is up to198.4 mm(with respect to MY165A).The coseismic displacement field revealed that the northwest region(hanging wall) moved upwards in comparison with the southeastern region(foot wall),suggesting that the seismogenic fault mainly underwent thrust faulting.By comparing the coseismic and interseismic vertical deformation fields,it was found that the mechanisms of this earthquake are consistent with the elastic rebound theory; the elastic strain energy(displacement deficit) accumulated before the Lushan earthquake was released during this quake.展开更多
基金supported by the National Natural Science Foundation of China (41631073)。
文摘We introduce a method of integrating Global Positioning System(GPS)and accelerometer data for high-rate seismogeodesy.This method is based on the GPS variometric approach which can obtain seismic waves in real time using only the readily available broadcast products and a single receiver.Collocated 5 Hz GPS and 200 Hz accelerometer data from the 2010 M_(W) 7.2 EI Mayor-Cucapaph earthquake were analyzed to verify the effectiveness of this method.Results reveal that this method can provide broadband and more accurate displacements qualified to avoid the baseline drifting caused by strong motion.Moreover,this method can effectively avoid the aliasing problem present in the 5-Hz GPS waveforms.We therefore conclude that this method can be a powerful tool to capture seismic waves in real time,which is crucial to tsunami early warning and earthquake rapid response.
基金supported by National Natural Science Foundation of China(41074016)
文摘Based on Continuous GPS (CGPS) observation data of the Crustal Movement Observation Network of China (CMONOC) and the Sichuan Continuous Operational Reference System (SCCORS),we calculated the horizontal coseismic displacements of CGPS sites caused by the 2013 Lushan Mw 6.6 earthquake.The results indicate that the horizontal coseismic deformations of CGPS stations are consistent with thrust-compression rupture.Furthermore,the sites closest to the epicenter underwent significant coseismic displacements.Three network stations exhibited displacements greater than 9 mm (the largest is 20.9 mm at SCTQ),while the others were displaced approximately 1-4 mm.
文摘By inverting GPS data recorded at stations of the Crustal Movement Observation Network of China(CMONOC)near the 2013 Lushan Ms7.0 earthquake,we found a horizontal displacement of 22 mm at a site about 32 km SW of the epicenter and vertical displacements of as much as 12.4 mm at several sites.The vertical displacements were generally uplift on the west side of the nearby Longmenshan fault zone and subsidence on the east side.We also found coseismic ionospheric disturbances about 0.5 to 0.9 TECU in amplitude that lasted for about one hour.
基金supported by the Earthquake Public Welfare Scientific Research Special Project (No.201408014)
文摘Usually, GPS observation provides direct evidence to estimate coseismic displacement. However, GPS stations are scattered, sparse and cannot provide a detailed distribution of coseismic displacement. Strong ground motion records share the same disadvantages as GPS in estimating coseismic displacement. Estimations from In SAR data can provide displacement distributions; however, the resolution of such methods is limited by the analysis techniques. The paper focuses on estimating the coseismic displacement of the M_S7.0 Lushan earthquake on April 20, 2013 using a simulation of the wave field based on the elastic wave equation instead of a quasi-static equation. First, the media and source models were constructed by comparing the simulated velocity and the record velocity of the ground motion. Then simulated static displacements were compared with GPS records. Their agreement validates our results. Careful analysis of the distribution of simulated coseismic displacements near the fault reveals more details of the ground motion. For example, an uplift appears on the hanging wall of the fault,rotation is associated with the horizontal displacement, the fault strike and earthquake epicenter provide the main control on motion near the faults, and the motion on the hanging wall is stronger than that on the footwall. These results reveal additional characteristics of the ground motion of the Lushan earthquake.
基金provided by the Japan Aerospace Exploration Agency through the research project PER3A2N162supported by the National Natural Science Foundation of China (Grant Nos.42021003 and 41974017)。
文摘In mountainous areas,landslides induced by destructive earthquakes are one of the main causes of human casualties,which is an important link in the chain of earthquake hazards.Earthquake-triggered landslides are mainly controlled by three factors,namely seismic property,topography,and geology.Many studies have been conducted on these controlling factors of earthquake-triggered landslides.However,little is known about the effect of coseismic displacement on the distribution of landslides under different slope aspects and slope angles,hindering our understanding of the mechanism of inducing landslides by the combination of surface displacement and slope geometry at the local scale and leading to controversial opinions about the abnormal number of earthquake-triggered landslides in several cases.Here,we took the 2008 Wenchuan M_(w) 7.9 earthquake in China,the 2015 Gorkha M_(w) 7.8 earthquake in Nepal,and the 2016 Kaikōura M_(w) 7.8 earthquake in New Zealand as examples to investigate the relationship between the distribution of large earthquake-triggered landslides and the three-dimensional (3D)coseismic displacement field.We divided the landslide-prone area around the epicenter into regular grids and calculated the 3D coseismic displacement in each grid according to the radar satellite images and slip distribution model.Then,the 3D coseismic displacement was projected to two coordinate systems related to the slope where the landslides were located for statistical analysis.We determined that the surface uplift perpendicular to the slope is more likely to induce landslides,particularly when combined with large slope angles.Meanwhile,the number of landslides will be significantly reduced where the subsidence occurs.Regardless of uplift or subsidence,landslides are more likely to occur when the direction of coseismic horizontal displacement is far from the slope.The larger the slope angles are,the greater the effects of horizontal displacement and slope aspect.A dominant slope aspect also exists for earthquake-triggered landslides,which is different from the mean slope aspect calculated from the background topography.This dominant aspect angle is related to the focal mechanism and striking angle of surface rupture.These results indicate that we can simulate the 3D coseismic displacement field from known fault location and earthquake mechanism and combine the topographic data for landslide risk assessment in earthquake-prone mountainous areas to minimize the damage caused by possible earthquake-triggered landslides.
基金supported by the National Natural Science Foundation of China project (No. 42372339)the China Geological Survey Project (Nos. DD20221816, DD20190319)。
文摘On September 5, 2022, a magnitude Ms 6.8 earthquake occurred along the Moxi fault in the southern part of the Xianshuihe fault zone located in the southeastern margin of the Tibetan Plateau,resulting in severe damage and substantial economic loss. In this study, we established a coseismic landslide database triggered by Luding Ms 6.8 earthquake, which includes 4794 landslides with a total area of 46.79 km^(2). The coseismic landslides primarily consisted of medium and small-sized landslides, characterized by shallow surface sliding. Some exhibited characteristics of high-position initiation resulted in the obstruction or partial obstruction of rivers, leading to the formation of dammed lakes. Our research found that the coseismic landslides were predominantly observed on slopes ranging from 30° to 50°, occurring at between 1000 m and 2500 m, with slope aspects varying from 90° to 180°. Landslides were also highly developed in granitic bodies that had experienced structural fracturing and strong-tomoderate weathering. Coseismic landslides concentrated within a 6 km range on both sides of the Xianshuihe and Daduhe fault zones. The area and number of coseismic landslides exhibited a negative correlation with the distance to fault lines, road networks, and river systems, as they were influenced by fault activity, road excavation, and river erosion. The coseismic landslides were mainly distributed in the southeastern region of the epicenter, exhibiting relatively concentrated patterns within the IX-degree zones such as Moxi Town, Wandong River basin, Detuo Town to Wanggangping Township. Our research findings provide important data on the coseismic landslides triggered by the Luding Ms 6.8 earthquake and reveal the spatial distribution patterns of these landslides. These findings can serve as important references for risk mitigation, reconstruction planning, and regional earthquake disaster research in the earthquake-affected area.
基金supported by grants from the National Natural Science Foundation of China(Grant No.sU2139205,41774011,41874011)the National Key Research and Development Program of China(Grant No.2018YFC1503605)。
文摘Three M_(W)>7.0 earthquakes in 2020-2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone,including the Mw7.8 Simeonof thrust earthquake on July 22,2020,the M_(W)7.6 Sand Point strike-slip earthquake on October 19,2020,and the M_(W)8.2 Chignik thrust earthquake on July 29,2021.The spatial and temporal proximity of these three earthquakes prompts us to probe stress-triggering effects among them.Here we examine the coseismic Coulomb stress change imparted by the three earthquakes and their influence on the subduction interface.Our results show that:(1)The Simeonof earthquake has strong loading effects on the subsequent Sand Point and Chignik earthquakes,with the Coulomb stress changes of 3.95 bars and 2.89 bars,respectively.The Coulomb stress change caused by the Sand Point earthquake at the hypocenter of the Chignik earthquake is merely around 0.01 bars,suggesting the negligible triggering effect on the latter earthquake;(2)The triggering effects of the Simeonof,Sand Point,and Chignik earthquakes on aftershocks within three months are not well pronounced because of the triggering rates of 38%,14%,and 43%respectively.Other factors may have played an important role in promoting the occurrence of these aftershocks,such as the roughness of the subduction interface,the complicated velocity structure of the lithosphere,and the heterogeneous prestress therein;(3)The three earthquakes caused remarkable coseismic Coulomb stress changes at the subduction interface nearby these mainshocks,with an average Coulomb stress change of 3.2 bars in the shallow region directly inwards the trench.
文摘In the case of reverse drag of normal faulting, the displacement and horizontal extension are determined based on the established equations for the three mechanisms: rigid body, vertical shear and inclined shear. There are three sub-cases of basal detachment for the rigid body model: horizontal detachment, antithetic detachment and synthetic detachment. For the rigid body model, the established equations indicate that the total displacement on the synthetic base (D<sub>t2</sub>) is the largest, that on the horizontal base (D<sub>t1</sub>) is moderate, and that on the antithetic base (D<sub>t3</sub>) is the smallest. On the other hand, the value of (D<sub>t1</sub>) is larger than the displacement for the vertical shear (D<sub>t4</sub>). The value of (D<sub>t1</sub>) is larger than or less than the displacement for the inclined shear (D<sub>t5</sub>) depending on the original fault dip δ<sub>0</sub>, bedding angle θ, and the angle of shear direction β. For all original parameters, the value of D<sub>t5</sub> is less than the value of D<sub>t4</sub>. Also, by comparing three rotation mechanisms, we find that the inclined shear produces largest extension, the rigid body model with horizontal detachment produces the smallest extension, and the vertical shear model produces moderate extension.
基金supported by the National Magnetic Confinement Fusion Energy R&D Program of China(Nos.2022YFE03030001,2022YFE03020004,2022YFE 03050003)National Natural Science Foundation of China(Nos.12275310,11975275,12175277,11975271)+2 种基金the Science Foundation of Institute of Plasma Physics,Chinese Academy of Sciences(No.DSJJ-2021-01)the Collaborative Innovation Program of Hefei Science Center,Chinese Academy of Sciences(No.2021HSC-CIP019)the Users with Excellence Program of Hefei Science Center,Chinese Academy of Sciences(Nos.2021HSC-UE014,2021HSCUE012)。
文摘A gas puff imaging(GPI)diagnostic has been developed and operated on EAST since 2012,and the time-delay estimation(TDE)method is used to derive the propagation velocity of fluctuations from the two-dimensional GPI data.However,with the TDE method it is difficult to analyze the data with fast transient events,such as edge-localized mode(ELM).Consequently,a method called the spatial displacement estimation(SDE)algorithm is developed to estimate the turbulence velocity with high temporal resolution.Based on the SDE algorithm,we make some improvements,including an adaptive median filter and super-resolution technology.After the development of the algorithm,a straight-line movement and a curved-line movement are used to test the accuracy of the algorithm,and the calculated speed agrees well with preset speed.This SDE algorithm is applied to the EAST GPI data analysis,and the derived propagation velocity of turbulence is consistent with that from the TDE method,but with much higher temporal resolution.
文摘The estimation of residual displacements in a structure due to an anticipated earthquake event has increasingly become an important component of performance-based earthquake engineering because controlling these displacements plays an important role in ensuring cost-feasible or cost-effective repairs in a damaged structure after the event.An attempt is made in this study to obtain statistical estimates of constant-ductility residual displacement spectra for bilinear and pinching oscillators with 5%initial damping,directly in terms of easily available seismological,site,and model parameters.None of the available models for the bilinear and pinching oscillators are useful when design spectra for a seismic hazard at a site are not available.The statistical estimates of a residual displacement spectrum are proposed in terms of earthquake magnitude,epicentral distance,site geology parameter,and three model parameters for a given set of ductility demand and a hysteretic energy capacity coefficient in the case of bilinear and pinching models,as well as for a given set of pinching parameters for displacement and strength at the breakpoint in the case of pinching model alone.The proposed scaling model is applicable to horizontal ground motions in the western U.S.for earthquake magnitudes less than 7 or epicentral distances greater than 20 km.
基金Supported by the Joint Fund Project of the National Natural Science Foundation of China(U22B2075).
文摘A seepage-geomechanical coupled embedded fracture flow model has been established for multi-field coupled simulation in tight oil reservoirs,revealing the patterns of change in pressure field,seepage field,and stress field after long-term water injection in tight oil reservoirs.Based on this,a technique for enhanced oil recovery(EOR)combining multi-field reconstruction and combination of displacement and imbibition in tight oil reservoirs has been proposed.The study shows that after long-term water flooding for tight oil development,the pressure diffusion range is limited,making it difficult to establish an effective displacement system.The variation in geostress exhibits diversity,with the change in horizontal minimum principal stress being greater than that in horizontal maximum principal stress,and the variation around the injection wells being more significant than that around the production wells.The deflection of geostress direction around injection wells is also large.The technology for EOR through multi-field reconstruction and combination of displacement and imbibition employs water injection wells converted to production and large-scale fracturing techniques to restructure the artificial fracture network system.Through a full lifecycle energy replenishment method of pre-fracturing energy supplementation,energy increase during fracturing,well soaking for energy storage,and combination of displacement and imbibition,it effectively addresses the issue of easy channeling of the injection medium and difficult energy replenishment after large-scale fracturing.By intensifying the imbibition effect through the coordination of multiple wells,it reconstructs the combined system of displacement and imbibition under a complex fracture network,transitioning from avoiding fractures to utilizing them,thereby improving microscopic sweep and oil displacement efficiencies.Field application in Block Yuan 284 of the Huaqing Oilfield in the Ordos Basin has demonstrated that this technology increases the recovery factor by 12 percentage points,enabling large scale and efficient development of tight oil.
基金funded by the Basic Research Program of the Institute of Earthquake Forecasting,China Earthquake Administration(Grant Nos.CEAIEF20220102,2021IEF0505,and CEAIEF2022050502)the National Natural Science Foundation of China(Grant Nos.42072248 and 42041006)the National Key Research and Development Program of China(Grant Nos.2021YFC3000601-3 and 2019YFE0108900)。
文摘Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface ruptures and secondary disasters surrounding the epicentral area is important for post-earthquake emergency and disaster assessments.High-resolution Maxar and GF-2 satellite data were used after the events to extract the location of the rupture surrounding the first epicentral area.The results show that the length of the interpreted surface rupture zone(part of)is approximately 75 km,with a coseismic sinistral dislocation of 2-3 m near the epicenter;however,this reduced to zero at the tip of the southwest section of the East Anatolia Fault Zone.Moreover,dense soil liquefaction pits were triggered along the rupture trace.These events are in the western region of the Eurasian Seismic Belt and result from the subduction and collision of the Arabian and African Plates toward the Eurasian Plate.The western region of the Chinese mainland and its adjacent areas are in the eastern section of the Eurasian Seismic Belt,where seismic activity is controlled by the collision of the Indian and Eurasian Plates.Both China and Türkiye have independent tectonic histories.
文摘Objective:To observe the clinical effect of articular cavity injection combined with bite splint therapy for the treatment of anterior disc displacement without reduction(ADDWoR).Methods:The research subjects for this study were 30 patients with ADDWoR treated in the temporomandibular joint specialist outpatient clinic from November 2018 to November 2019,with a disease duration of 1 to 6 months.The treatment group was treated with an articular cavity injection of sodium hyaluronate+bite splint.The control group was treated with a simple articular cavity injection of sodium hyaluronate.The two groups were followed up once every 2 weeks to evaluate the treatment effect and observe the clinical efficacy of the two groups.Statistical analysis was carried out using SPSS 24.0.t-test and general linear regression analysis were carried out to compare the data of both groups,andχ^(2)-test and binary logistic regression analysis were performed for pain index comparison.Results:There was no significant difference in terms of the efficacy of the treatment received by both groups.The mouth opening and joint pain of patients in both groups were significantly improved after treatment(P<0.001).Conclusion:Articular cavity injection of sodium hyaluronate and occlusal splint therapy are both effective and safe methods for treating ADDWoR.
基金supported by the National Key Basic Research and Development Program of China(Grant No.2018YFC1503603)the National Natural Science Foundation of China(Grant No.42030112)+3 种基金the Nature Science Foundation of Hunan Province(Grant No.2020JJ2043)the Project of Innovation-driven Plan of Central South University(Grant No.2019CX007)the Fundamental Research Funds for the Central Universities of Central South University(Grant Nos.2018zzts684 and 2019zzts011)the Hunan Provincial Innovation Foundation For Postgraduate(Grant No.CX20190067)。
文摘On 22 nd May 2021(local time),an earthquake of M_(s)7.4 struck Maduo county in Qinghai Province,China.This was the largest earthquake in China since the 2008 Wenchuan earthquake.In this study,ascending/descending Sentinel-1 and advanced land observation satellite-2(ALOS-2)synthetic aperture radar(SAR)images were used to derive the three-dimensional(3-D)coseismic displacements of this earthquake.We used the differential interferometric SAR(In SAR,DIn SAR),pixel offset-tracking(POT),multiple aperture In SAR(MAI),and burst overlap interferometry(BOI)methods to derive the displacement observations along the line-of-sight(LOS)and azimuth directions.To accurately mitigate the effect of ionospheric delay on the ALOS-2 DIn SAR observations,a polynomial fitting method was proposed to optimize range-spectrum-split-derived ionospheric phases.In addition,the 3-D displacement field was obtained by a strain model and variance component estimation(SM-VCE)method based on the high-quality SAR displacement observations.Results indicated that a left-lateral fault slip with the largest horizontal displacement of up to 2.4 m dominated this earthquake,and the small-magnitude vertical displacement with an alternating uplift/subsidence pattern along the fault trace was more concentrated in the near-fault regions.Comparison with the global navigation satellite system data indicated that the SM-VCE method can significantly improve the accuracy of the displacements compared to the classical weighted least squares method,and the incorporation of the BOI displacements can substantially benefit the accuracy of north-south displacement.In addition to the displacements,three coseismic strain invariants calculated based on the strain model parameters were also investigated.It was found that the eastern and western parts of the faults suffered more significant strains compared with the epicenter region.
基金the National Key Basic Research Program (Grant No. G1998040703) and the CAS Knowledge Innovation Key Project. The ERS-1/2 SAR data were provided by ESA for the ERS Project (ERS A03-374).
文摘The coscismic deformation produced by 1998 earthquake (M8 = 6.2) in Zhangbei-Shangyi of northern China is measured by the differential synthetic aperture radar interferometry (D-InSAR) technique using the European Remote Sensing satellite (ERS) SAR data. Interferograms are constructed from the ERS-1/2 SAR data by the three-pass method. The line-of-sight displacement map indicates that the deformation center of the earthquake is located at E114°20’, N40°57’, with the maximum uplift of 25 cm. The extent of the displacement is around 300 km2. The focal mechanism and earthquake-induced structures are analyzed based on the spatial distribution of the deformation. The results give new insights into the seismic mechanism study.
基金supported by the State Key Laboratory of Earthquake Dynamics (LED2009A02)the National Key Infrastructure Project "Tectonic and Environmental Observation Network in China"
文摘Analysis of GEONET observations covering the entire territory of Japan shows that the great Tohoku-oki earthquake that occurred on March 11, 2011 off the east coast of Honshu in Japan caused an eastward movement of the northern part of the island by as much as 5.3 m. The GPS data from TEONET in China were used to derive far-field coseismic displacements and to assess the impact of the Tohoku-oki earthquake on crustal deformation in eastern China. The results reveal that the coseismic horizontal displacements induced by the earthquake are the level of millimeters to centimeters in North and Northeast China, with a maximum of 35 mm. Strain analysis also indicates that the earthquake resulted in an increase in the tensile strain on the north-northeast trending faults in North and Northeast China. The tensile strain imposed on the Yilan-Yitong and Dunhua-Mishan faults is more significant than that imposed on the faults in North China; the maximum normal strain reaches about 40 nano-strain. Considering that the static Coulomb stress loaded on the faults is limited, its effect on the regional seismic activity may not be significant.
基金supported by the National Key Technology R&D Program in the 12th Five-year Plan of China(2012BAK19B01)the National Natural Science Foundation of China(41274008 and 41104004)+2 种基金the Basic Research Project of Institute of Earthquake Science of China Earthquake Administration(2011IES010101)the Specific Fund of Seismic Industry of China Earthquake Administration(201008007)the Scientific Investigation Projects of the Wenchuan and Lushan Earthquakes,CEA
文摘This paper presents the coseismic displacement and preseismic deformation fields of the Lushan MS7.0 earthquake that occurred on April 20,2013.The results are based on GPS observations along the Longmenshan fault and within its vicinity.The coseismic displacement and preseismic GPS results indicate that in the strain release of this earthquake,the thrust rupture is dominant and the laevorotation movement is secondary.Furthermore,we infer that any possible the rupture does not reach the earth’s surface,and the seismogenic fault is most likely one fault to the east of the Guanxian-Anxian fault.Some detailed results are obtainable.(1)The southern segment of the Longmenshan fault is locked preceding the Lushan earthquake.After the Wenchuan earthquake,the strain accumulation rate in the southeast direction accelerates in the epicenter of the Lushan earthquake,and the angle between the principal compressional strain and the seismogenic fault indicates that a sinistral deformation background in the direction of the seismogenic fault precedes the Lushan earthquake.Therefore,it is evident that the Wenchuan MS8.0 earthquake accelerated the pregnancy of the Lushan earthquake.(2)The coseismic displacements reflected by GPS data are mainly located in a region that is 230 km(NW direction)×100 km(SW direction),and coseismic displacements larger than 10 mm lie predominantly in a100-km region(NW direction).(3)On a large scale,the coseismic displacement shows thrust characteristics,but the associated values are remarkably small in the near field(within 70 km)of the earthquake fault.Meanwhile,the thrust movement in this70-km region does not correspond with the attenuation characteristics of the strain release,indicating that the rupture of this earthquake does not reach the earth’s surface.(4)The laevorotation movements are remarkable in the 50-km region,which is located in the hanging wall that is close to the earthquake fault,and the corresponding values in this case correlate with the attenuation characteristics of the strain release.
文摘Based on continuous GPS observations within China as well as global GPS tracking network, a calculation has been made of far-field coseismic displacements associated with the December, 2004 (Mw = 9.3) and March, 2005 (Mw = 8.7) earthquakes. The far-field coseismic displacements are associated with the 2004 shock range more than 6000―7000 km in both north-south and east-west dimensions, and depict an undulated wave pattern of contraction and extension. The coseismic displacements associ-ated with the 2005 event, however, are distributed near the epicentral region, and the event itself may be an aftershock of the 2004 earthquake.
基金supported by National Special Fund for Earthquake Scientific Research in Public Interest(201408014,201208009)the National Natural Science Foundation of China(41174083)
文摘By using precise leveling data observed between 1985 and 2010 across the south section of the Longmenshan fault zone,and eliminating the coseismic displacements caused by the Wenchuan Ms 8.0 earthquake,the interseismic vertical deformation field was obtained.The result shows that the Lushan region,located between the Shuangshi–Dachuan fault(front range of the Longmenshan fault) and the Xinkaidian fault(south section of the Dayi fault),is situated in the intersection zone of positive and negative vertical deformation gradient zones,indicating that this zone was locked within 25 years before the Lushan earthquake.Based on leveling data across the rupture zone surveyed between 2010 and 2013,and by eliminating the vertical deformation within 3 years before the earthquake,the coseismic vertical displacement was derived.The coseismic vertical displacement for the benchmark DD35,which is closest to the epicenter,is up to198.4 mm(with respect to MY165A).The coseismic displacement field revealed that the northwest region(hanging wall) moved upwards in comparison with the southeastern region(foot wall),suggesting that the seismogenic fault mainly underwent thrust faulting.By comparing the coseismic and interseismic vertical deformation fields,it was found that the mechanisms of this earthquake are consistent with the elastic rebound theory; the elastic strain energy(displacement deficit) accumulated before the Lushan earthquake was released during this quake.
基金supported by the 973 Project of China (No.2013CB733303)the National Natural Science Foundation of China (No.41474093)the Open Research Fund Program of the Key Laboratory of Geospace Environment and Geodesy of Ministry of Education,China (No.12-02-08)
